ABSTRACT
Many pesticides partially evaporate during and after application and therefore enter into the lower troposphere. Their fate in this compartment of the environment depends on physical distribution and chemical degradation processes. The most important distribution process which influences the photochemical degradation occurs between the gas phase and the particle phase and can be approximately described by Junge's formula. The principle of measurement consists of measuring the decay of the test substance and at least one reference compound dissolved in Freon 113 which is saturated with H2O2. In order to estimate the degradation behavior of compounds in the atmosphere, we have to know the rate constants of direct and indirect photochemical reactions acting as sinks in the gas phase and in the adsorbed state. The semivolatile organic compounds (SOC) may occur either in the gas phase or in the adsorbed state, depending on temperature, particle surface, and vapor pressure.
